Conventional pipeline maintenance and repair methods comprise first discontinuing normal pipeline operations, then isolating the section of pipeline to be repaired or maintained by closing a valve or providing some other type of seal in the pipeline, and then draining liquids or blowing down gases within the isolated section of pipeline. Once the product is removed from the isolated section of pipeline, repair and/or maintenance operations may then be performed. These operations may include cutting and replacing a leaking section of pipeline and/or installing permanent devices in the pipeline, such as a valve. When making such permanent installations in the pipeline, a structural integrity test, such as a hydrostatic test, may be performed thereafter, in which case the water used in the test must be drained, and in some cases, the pipeline is also dried depending upon the pipeline service. Finally, the pipeline can be re-commissioned with product and normal operations resumed.
These conventional methods are both time-consuming and expensive due to the discontinued pipeline operations, the loss of product that may be incurred due to draining or blowing down, and the time and expense associated with cutting into the pipeline to make the actual repair and/or perform the maintenance operation, such as replacing a leaking section of pipeline or installing a permanent device.
To address some of these inefficiencies, a pipeline isolation pig has been developed that may be used to isolate a section of pipeline so that maintenance and repair operations may then be performed. The pipeline isolation pig is a remote-controlled device that may be positioned at any desired location within the pipeline to isolate a section of pipeline so as to minimize the amount of product to drain or blow down before performing the work. It may be launched into a pipeline and pushed along by the product while being tracked to its intended destination. Then the pipeline isolation pig may be locked into position to completely seal across the pipeline. Drawbacks to the pipeline isolation pig is that it does not act as a permanent repair device, and it does not permit product flow therethrough. Instead it seals the pipeline in such a way that the seal is only removable by removing the pipeline isolation pig entirely from the pipeline. Hence, after the repair and/or maintenance operations are complete, the pipeline isolation pig must be removed from the pipeline to permit normal pipeline operations to resume.
Therefore, a need exists for a more efficient, less costly, and optionally permanent repair apparatus, and methods of performing pipeline maintenance, leak repair, and installation of permanent devices.